Process of making ammonia from calcium cyanamid.



E STAES PATENT WALTER S. LANDIS, OF NIAGARA FALLS, NEW YORK, ASSIGNQR TOAMERICEJN CYANAMI'D COMPANY, OE NASHVILLE, TENNESSEE,-i A CORPORATIQN (1MAINE.

PROCESS OF MAKING AMMONIA FROM CALCIUM CYANAMID.

No Drawing.

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lie it known that l, \VAL'rEn S. Lawns, a citizen of the United States.residing at Niagara Falls. in the county of Niagara and State of NewYork. have invented certain new and useful Improvements in Processes ofMaking Ammonia from Calcium Cyanamid: and I do hereby declare thefollowing to be a full. clear. and exact description of the invention,such as will enable others skilled in the art to which it appertains tomake and use the same.

This invention relates to a process of making ammonia from calciumcyanamid and has for its object to provide a procedure which will bemore etlicient and less costly than those heretofore pro )osed.

ll'ith these and other objects in view the invention consists in thenovel steps and combimititms of steps constituting my process, all aswill be more fully hereinafter disclosed and particularly pointed out inthe claims.

As is well. known calcium cyanainid in its crude state consists of.approximately (30% calcium cyanamid. CaCN 25')? lime. C210. 12)? carbonin the form of graphite. add theremainder of various impurities pickedup in the process from the raw materials on tcring into its manufacture;these latter impurities being of no importance to this process. ()ntreating calcium cyanamid with water a portion of the CaQN passes overinto ammonia, according to the following equation c ;'anamid has beenthus used for a. long time as a commercial souroeof ammonia.

However, this high temperaturedoes not prevent a portion of thecyananrid deconr posing into dicyandlamld and VELllOllS otherSpecification of Letters Patent.

Application filed June 18 1914.

composed into ammonia under the most skil- Pa-tented Aug. it Serial No.845.970.

organic compounds, and there is always considerable loss of nitrogen.even under t best conditions of carrying out the reaction, in the mannerdescribed. This largely due to the formation of dicyandiamidl whichcompound does not seem to broken up into ammonia in a strongly al kalinesolution in the autoclave. probably because the alkali present. calciumhydrate, (a(()ll). is not sulticiently strong to cause a decompositionof the dicyandiamid. it best, working oh a large scale in the autoclaveholding 2 to (3 tons of cyanamid at an operation, it has been found thatonly from 5'to 90% of the calcium cyanamid deful production andoperation.

I have discovered however, that it a small quantity of alkali. such assodium lhfthmxid, or potassium hydroxid. is introduced with the calciumcyanamid into the autoclave, a

- much more el'ticicnt transtormation into amtassium hydroxid or similarstrong alcalis of this kind.

The, most economical amount of sodium hydro id to be added is somewhatindeterminate inasmuch as the more-that added up to a certainproportion. the better will be the yield oi ammonia, but for commercialreasons. as well as for theoretical reasons. it

loss is is found best to restrict the addition of ai- Y kali in allcases to less than 10% of the weight of the crude calciun'i cyanamidcharged into the autoclave. But again, smaller quantities as forinstance 2' to 4%, give very good results in increasing the yield ofammonia from the cyanamid.

Inasmuch asthere is a large amount of free lime present in the crudecyanamid charged into the autoclave it is not neces sary that suchalkali addition he made in the form of hydroxid, but I can use cheapersalts like potash, soda ash, or sulfates of these elements, and haveeven obtained some fairly-promising results from-the addition ofchlorids. It is, of course possible also where commercial conditionspermit, to use jmi'xtures of these compounds, though I have found thatin all the large number of possible mixtures there should always betions inasmuch as the salts can be mixed in the grinding mill with thecalcium cyanamid, or can be added in-the form of solution to the chargeentering into the autoclave, since all of them are soluble in water.

am aware that the British Patent #18207 of 1911 has been grantedt-o,Lyd-

holm, wherein he uses one part by weight of lime nitrogen to two partsby Weight of an alkali salt, and wherein the patentee states that 99 percent. of the total nitrogen contained inthe nitro-lime were set free in15 minutes.v I have, however, carried out the process of Lydholmfollowihg his specification, and have been unable to attain the resultshe states. Large scale tests have shown that it is an. error to supposethat the alkali salts are causticized by the free lime present, exceptto a small extent, and therefore it has even been found necessary inmany cases toadd free lime, usually about 50 per cent. of the amount-ofsaid salts employed to assist in this causticizing action.

In other words, I have found it an unnecessary waste of material toemploy more of such salts than the free lime in the mixture willcausticize, and therefore, any such proportions as those givenby Lydholminvolve many times the amount of said salts that is necessary for thesuccess of the process. Owing to this state of facts, I have discovered.that in the majority of cases, a

quantity of such salts notexceeding 3 per cent. or 1: per cent. or 5 percent. of the Weight of the lime nitrogen is all that is needed, and thatwhen such quantities are used, in my process efficiencies are readilyattained that are much greater than any I have been able. to attain whenfollowing Lydholms ill. losure.

the autoclave, and therefore I do not wish to be limited to the abovedisclosure except as may be required by .the claims.

\Vhat I claim is:

1. The process of producing ammonia fromcommercial calcium cyananiidwhich consists in treating said cyanamid with steam and adding than 10%of the weight of said cyanamid of a salt having an alkaline reactionthat will reduce the amount of dicyandiamid which would be otherwiseproduced if said salt be not added, substantially as described.

2. The process of producing ammonia from commercial calcium cyanamidwhich consists in treating said cyanamid with steam above 120. C. in thepresence of less than 10% of the weight of said cyananiid of salt havinga restraining action on the simultaneous production of dicyandiamid,substantially as described.

The process of producing ammonia from commercial cyariamid whichconsists in treating said cyanamid with steam above 130 C. and addingless than 10% by weight of a salt having an alkaline reaction to themass to reduce the formation of dicyandiamid, substantially asdescribed.

"4. The process of producing ammonia from commercial calcium cyanamidwhich consists in adding less than 10% by weight of a salt of an alkalito said cyanamid and treating the same with steam, substantially asdescribed.

5. The process of increasing the yield of ammonia from commercialcalcium cyana mid when treated with steam, which con-, sists in treatingsaid cyanamid with steam in the presence of less than 6% by'weight of asalt of an alkali, substantially as de-' scribed. j

In testimony whereof I'affix my signature, in presefrce of twowitnesses.

IVALTER S. LAXDIS.

Witnesses S. HANNA, J. L. DOLAN.

